Fructose Component Research Articles

The metabolic properties of spermatozoa from the epididymis of the tammar wallaby, Macropus eugenii

The utilization of various substrates by sperm from the cauda epididymidis of the tammar was examined because the major naturally occurring sugar in the semen of this species is N-acetyl-D-glucosamine (NAG) and not fructose, as in eutherian mammals. The sperm displayed a high level of endogenous respiration that supported motility for relatively prolonged periods of time in vitro. They also metabolised exogenous 14C-labelled glucose, NAG, sucrose, and acetate through glycolytic and/or oxidative processes to produce lactate and 14CO2 at varying rates. The rate of uptake of NAG by tammar sperm was about four times greater than that of other substrates. Glucose and/or NAG stimulated the rate of oxygen consumption by about 20%, but acetate stimulated oxygen consumption by more than 40%. The most striking findings were that NAG almost completely inhibited the oxidation of glucose and sucrose by the sperm and depressed the uptake of glucose, 3-O-methylglucose, and sucrose. Acetate oxidation also was inhibited by NAG, but only by about 50%. Tammar sperm generated substantial amounts of free glucose during incubation with NAG, but this and the inhibitory effects of NAG on glucose oxidation were not mimicked by rat sperm. It is proposed that tammar sperm fail to oxidise glucose in the presence of NAG because of the rapid cellular uptake of NAG relative to glucose. Also, the intracellular glucose and acetate liberated from NAG would compete with exogenous glucose for processing in the Embden-Meyerhof and tricarboxylic acid (TCA) cycle pathways. It is also suggested that tammar sperm oxidise sucrose after extracellular hydrolysis into its glucose and fructose components. The biological implications of these metabolic and transport properties of tammar sperm have as yet to be determined. Mol. Reprod. Dev. 49:92–99, 1998. © 1998 Wiley-Liss, Inc.

The metabolic properties of spermatozoa from the epididymis of the tammar wallaby,Macropus eugenii

The utilization of various substrates by sperm from the cauda epididymidis of the tammar was examined because the major naturally occurring sugar in the semen of this species is N-acetyl-D-glucosamine (NAG) and not furctose, as in eutherian mammals. The sperm displayed a high level of endogenous respiration that supported motility for relatively prolonged periods of time in vitro. They also metabolised exogenous 14C-labelled glucose, NAG, sucrose, and acetate through glycolytic and/or oxidative processes to produce lactate and 14CO2 at varying rates. The rate of uptake of NAG by tammar sperm was about four times greater than that of other substrates. Glucose and/or NAG stimulated the rate of oxygen consumption by about 20%, but acetate stimulated oxygen consumption by more than 40%. The most striking findings were that NAG almost completely inhibited the oxidation of glucose and sucrose by the sperm and depressed the uptake of glucose, 3-O-methylglucose, and sucrose. Acetate oxidation also was inhibited by NAG, but only by about 50%. Tammar sperm generated substantial amounts of free glucose during incubation with NAG, but this and the inhibitory effects of NAG on glucose oxidation were not mimicked by rat sperm. It is proposed that tammar sperm fail to oxidise glucose in the presence of NAG because of the rapid cellular uptake of NAG relative to glucose. Also, the intracellular glucose and acetate liberated from NAG would compete with exogenous glucose for processing in the Embden-meyerhof and tricarboxylic acid (TCA) cycle pathways. It is also suggested that tammar sperm oxidise sucrose after extracellular hydrolysis into its glucose and fructose components. The biological implications of these metabolic and transport properties of tammar sperm have as yet to be determined.

Rapid preparation of samples for compositional sugar analysis of the "degraded polysaccharide" fraction of lipopolysaccharides from Vibrio cholerae.

A simple and rapid method was devised for direct isolation and fractionation of the "degraded polysaccharide" (DPS) fraction of O-antigenic (or endotoxic) lipopolysaccharides (LPS) directly from heat-killed Vibrio cholerae (O1 and non-O1) cells without separating the LPS. Neither phenol-water extraction nor ultracentrifuge is needed in this method. V. cholerae NIH 41 was used as standard. The cells (3-5 g wet weight) were heated in 5% acetic acid at 100 C for 1.5 hr. The acetic acid extract obtained as the supernatant by centrifugation was evaporated to dryness in vacuo, and the resultant residue was dissolved in 10 ml of distilled water. The solution was mixed with 2 volumes of acetone, and the supernatant obtained by centrifugation was mixed with 5 volumes of acetone and centrifuged. Fraction Sed. II was recovered as the precipitate, while the supernatant was evaporated to dryness in vacuo, yielding fraction Sup. III. Sed. II had a sugar composition that was identical, at least qualitatively, to that of DPS isolated from LPS of the corresponding strain except for the absence of a fructose component in the case of V. cholerae NIH 41, while instead Sup. III from V. cholerae NIH 41 contained fructose.

Fermentation patterns of gramicidin S formation by Bacillus brevis ATCC 9999 in high‐yielding synthetic medium

AbstractAddition of the gramicidin S (GS)‐constituent amino acids, other than the limiting precursor L‐phenylalanine, to the high‐yielding chemically defined F3/6 and G3/6 media, enhanced growth and volumetric GS‐production by Bacillus brevis ATCC 9999 considerably, but did not yield a higher specific GS‐production level. L‐Leucine alone could duplicate this stimulatory effect in G3/6 medium. Replacing the fructose component of F3/6 medium by these four amino acids yielded a high specific GS‐production level, but resulted in poor growth and low volumetric antibiotic production. Nutrient‐utilisation patterns in F3/6 medium revealed that B. brevis initially grew at the expense of L‐glutamine and L‐arginine. After a diauxic lag period, D‐fructose was consumed together with L‐histidine. L‐Proline was mainly used during the stationary phase. L‐Methionine was broken down gradually throughout the whole fermentation cycle. L‐Phenylalanine was metabolised only after GS formation started, and its disappearance was proportional to the amount of GS produced. Lowering the aeration rate caused an acidification of the medium, resulting in a slower and incomplete, although similar, nutrient‐utilisation pattern. At a controlled pH of 7.3, under lowered aeration, utilisation patterns were again comparable with those of a fully aerated fermentation, but GS levels were enhanced considerably (0.220 mg of GS mg−1 dry cell wt). Depending on environmental culture conditions, B. brevis also excreted different amino acids (L‐lysine, L‐alanine, L‐valine, L‐serine), which were in turn metabolised during late growth and differentiation stages. The onset of GS synthesis occurred on depletion of L‐glutamine and L‐arginine. Soluble GS synthetase 1 and 2 peaks coincided with ‘diauxic’ lag phases; this supported the idea that a high growth rate is incompatible with GS synthetase formation.

Effect of carbohydrate source and growth conditions on the production of lipoteichoic acid by Streptococcus mutans Ingbritt.

Streptococcus mutans Ingbritt was grown in a chemostat at defined dilution rates and pH values and under carbohydrate limitation. At a constant dilution rate of D = 0.1 h-1 and with either 0.5% glucose or 0.5% sucrose, the amounts of both cellular and extracellular lipoteichoic acid increased as the culture pH increased from 5.0 to 7.5. At a constant pH of 6.0, the amount of cellular lipoteichoic acid formed by cultures growing in 0.2% or 0.5% glucose was relatively constant over a range of dilution rates, although the amount of extracellular lipoteichoic acid formed in 0.2% glucose at intermediate dilution rates was less than that formed in 0.5% glucose. Organisms grown in 0.5% sucrose at pH 6.0 contained increasing amounts of cellular lipoteichoic acid as the dilution rate was increased. A comparison of the amounts of cellular lipoteichoic acid formed by organisms growing at D = 0.5 h-1 and pH 6.0 in glucose, sucrose, fructose, or mixtures of glucose and fructose in limiting amounts suggested that the enhanced production of lipoteichoic acic by sucrose-grown organisms was due to the fructose component. The culture fluids from both glucose- and sucrose-grown organisms contained detectable amounts of serotype c antigen, whereas glucose-grown cultures also contained significant amounts of an extracellular hexose-containing polymer.

A New Poultry Semen Extender: 2. Effect of the Diluent Components on the Fertilizing Capacity of Chicken Semen Stored at 5°C.

The major objective of this study was to assess the relationship of various components of the Beltsville Poultry Semen Extender (BPSE) to the maintenance of the fertilizing capacity of chicken semen stored at 5°C. A secondary objective was to test the effectiveness of certain chemical additives on maintaining the fertilizing capacity of stored semen.The data indicate that the components of the BPSE which contribute most to the preservation of semen were sodium glutamate and potassium phosphate. Also the high level of potassium in the BPSE was critical to the survival of spermatozoa during low temperature storage. Although the fructose component of the BPSE was not a significant factor during storage, attempts to substitute fructose with other carbohydrates resulted in a reduction in fertility. The addition of gentamicin sulfate (100 to 200 μg./ml.), or pasteurized milk (10% v./v.) to the BPSE did not significantly alter the fertilizing capacity of semen stored for 24 hr., whereas similar levels of whole egg, egg yolk, egg albumen or seminal plasma had a depressive effect.The data in this study clearly indicate that components of and additions to the BPSE were responsible for the maintenance of only about 50 to 60% of the fertilizing capacity of chicken semen stored for 24 hr. at 5° C.

Effect of longterm sucrose feeding on the activity of some enzymes regulating glycolysis, lipogenesis and gluconeogenesis in rat liver and adipose tissue

4- to 6-fold increases in the activity of liver pyruvate kinase (EC 2.7.1.40), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), NADP-malate dehydrogenase (EC 1.1.1.40) and acetyl-CoA carboxylase (EC 6.4.1.2), relative to liver protein concentration, were obtained in rats fed for 12 months on a 72% sucrose diet, as compared to rats kept on a standard laboratory chow. Feeding a 72% starch diet resulted in only 2- to 3-fold increases in the activities of these enzymes. The activity of liver 6-phosphogluconate dehydrogenase (EC 1.1.1.44) increased about 2-fold in the sucrose-fed rats and did not rise significantly on a starch diet. In adipose tissue, the activity of pentose shunt enzymes rose significantly only on the sucrose diet, whereas NADP-malate dehydrogenase rose 5-fold in sucrose and 2-fold in starch-fed rats. Fasting for 48 h resulted in a decrease in the activity of enzymes of glucose utilization and lipogenesis in the liver and adipose tissue, which on all diets was of s similar proportion with respect to the activity prior to fasting. The activity of most enzymes was reduced to 50–70% of the prefasting value; that of NADP-malate dehydrogenase decreased more pronouncedly. The activity of liver phosphoenolpyruvate carboxylase (EC 4.1.1 32) was slightly decreased on both starch and sucrose diets, whereas the activity of glucose-6-phosphatase (EC 3.1.3.9) was significantly increased in the sucrose-fed rats, indicating adaptation to gluconeogenesis from the fructose component. Each of the enzymes of gluconeogenesis responded to 48 h fasting with a rise in activity, the extent of which was not apparently related to the previous diet. The more extensive changes in enzyme activities on prolonged feeding of sucrose in comparison to starch are discussed with respect to the large share of the liver in the metabolism of carbohydrate intake on sucrose and to the role of the fructose component of sucrose in producing a pattern of adaptation of liver enzymes conducive to lipogenesis and glucose intolerance.

Biochemical studies on the formation and composition of dental plaque in relation to dental caries: extracellular polysaccharides.

Similar polysaccharides were extracted by dilute alkali from the matrix of the dental plaque of rats fed diets containing different sugars. The fructose components of the extracellular polysaccharides produced from sucrose by either of two streptococci or by the mixed oral flora were labile in the presence of oral bacteria.

Anaerobic respiration in latex ofHevea brasiliensis substrate and limiting factors

The site of anaerobic respiration in the latex is the serum. The main respiratory substrate is fructose. The CO2 formation in serum is increased by additional fructose on the average about 2.5–3 times. Glucose does not influence CO2 evolution by serum but slightly increases O2 consumption.With respect to sugars, latex serum contains essentially only sucrose and a low amount of raffinose. During the incubation of serum sucrose is hydrolysed, the fructose component is immediately utilized in respiration and glucose accumulates.The rate of CO2 formation in latex as influenced by fructose is negatively related to the rubber content of the latex. Latex with a high rubber content reacts only slightly or not at all on additional fructose.The main limiting factors of latex respiration and sugar utilization are the following: 1. The deficiency of substrate, due to low activity of β-fructofuranosidase. 2. The rate of glucose phosphorylation (D'Auzac, Jacob 1967). 3. Presumably the low activity of phosphoglucoisomerase. 4. The rubber content of the latex. 5. The concentration of CO2 in latex; this factor may be important in vivo, in the laticiferous system.

Radiorespirometrická studie využívání exogenní sacharosy, glukosy a fruktosy klíčícím pylem jabloně

The sequence of intensities with which pollen tubes utilize tested sugars from their 0.3 M solutions, is the following: sucrose >glucose >invert sugar > >fructose. The same sequence is maintained in sugar-agar media with the exception of the first two hours of incubation when sucrose, glucose and fructose are all utilized at a practically equal rate. During this period no pollen tubes were formed in the presence of fructose, in common with the sugar-free control, while in the presence of sucrose they reached a length of up to 450 µ. If sucrose was used as carrier for radioactive sugars, fructose-14C was utilized up to 12 times and glucose-14C as much as 6 times more actively than sucrose-14C. When sucrose + glucose or sucrose + fructose (in molar ratio 1 : 1) were used the pollen tubes utilized sucrose-14C at a slower rate than the corresponding monosaccharide and also at a slower rate than observed with sucrose alone. When glucose or fructose was used as carrier for sucrose-14C . the carbon dioxide-14C production by the pollen tubes was (during several time intervals of the experiment) several tens per cent higher than when sucrose served as carrier. Fructose is utilized preferentially from a medium with invert sugar. It thus appears that the capacity of the pollen enzymic systems for incorporating the sugars tested into their respiratory pathways is as follows: fructose >glucose > sucrose, this sequence being the opposite to that found for the intensity of their growth effect and to that established for the rate of their utilization, unless present in combination. The specific growth effect of sucrose cannot thus be due primarily to the rate of its absorption or to the intensty of its utilization. The rapid rate of utilization of sucrose alone is due to the more intense growth in the presence of sucrose. The results obtained further suggest that sucrose is utilized above all via its inversion when the fructose component is respired preferentially.

SYNTHESIS OF RADIOACTIVE SUCROSE BY TOBACCO LEAVES FROM C14 UNIFORMLY LABELLED GLUCOSE AND GLUCOSE-1-PHOSPHATE

Detached tobacco leaves were placed for six hours on solutions of C14 labelled glucose and glucose-1-phosphate. At the end of this time leaves were extracted with boiling 80% ethanol and the activities of their various carbohydrate fractions were determined. The specific activities of both glucose and fructose moieties of sucrose were found to be high and very close one to another, while that of the free fructose was low. From this it has been concluded that the fructose component of sucrose is derived from the glucose introduced and not from the free fructose present in leaves. Low activity in starch observed in photosynthesizing leaves indicates preferential transformation of the glucose introduced into sucrose and not into starch. Moreover, respiration of labelled glucose ought to produce labelled carbon dioxide, and after a period of photosynthesis, labelled starch. The isolated starch contained only a small amount of activity indicating that, in light, sugars were not utilized in respiration to any great extent. Moreover, they did in darkness, as the carbon dioxide evolved was very radioactive.

TRANSFORMATION OF SUGARS IN EXCISED BARLEY SHOOTS

Nelson and Auchincloss (10) working with potato tissue showed that sucrose is synthesized from glucose or fructose rather than from starch as has been supposed by some investigators. That such a conversion occurs in plant metabolism has also been shown by Virtanen and Nordlund (14) in red clover and wheat plants, and more recently by Hartt (3) in detached sugar cane leaves. Since sucrose, consisting of a glucose and fructose molecule, can readily be synthesized from either of these monosaccharides, it may be assumed that such synthesis involves a preliminary conversion of each of these hexose sugars into the other. The fructose component of the sucrose molecule exists in the furanose form (unstable ? form with the five-membered ring) and is different from the six-membered fructose (pyranose configuration) from which it can be synthesized. The plant apparently also possesses a mechanism to render this transformation possible. The fact that sucrose is synthesized when plants are artificially supplied with glucose or fructose can serve indirectly in the study of transformation of other hexoses in the plant into these monosaccharides. If, for example, synthesis of sucrose is observed after supplying the plant with mannose, it could be assumed that a preliminary conversion of the latter into glucose and fructose must take place before the synthesis of sucrose occurs. The hexoses that are known to occur naturally in plants are: d-glucose, d-fructose, d-mannose, and dgalactose ; of these the last two have not been detected in the free state and are found in plants only as units in polysaccharides. If, as it is generally assumed, some form of glucose is the first product of photosynthesis, the plant should possess a mechanism whereby this molecule is transformed into mannose or galactose before the synthesis of the corresponding polysaccharide can be possible. In this investigation, using the infiltration method (8), the following compounds were artificially supplied to barley plants : d-glucose, d-fructose, d-mannose, d-galactose, sucrose, lactose, maltose, 1-arabinose, d-xylose, mannitol, sorbitol, gluconic acid, pyruvic acid, and glyceric aldehyde. The increase of sucrose was observed after certain periods of time to determine the ability of the plant to transform these compounds into glucose or fructose and, if possible, to ascertain the mechanism of this transformation.